The present invention relates to an assembly for securely mounting a sensor to an image-acquisition device capable of pivoting, and, in particular for securely mounting a sensor to a C-arm or some other C-shaped fluoroscope.
Referring to FIG. 1, an image-acquisition device 100 can be used for simultaneous real-time image acquisition and intrabody navigation of a probe, such as a catheter 105. Catheters may be employed for diagnostic purposes, e.g., by retrieving samples of tissue, or for therapeutic purposes, e.g., ablation by radiofrequency waves emitted by at least one electrode contained in the catheter. In either case, tracking of the catheter 105 as it is navigated through the body of a patient is of great importance.
To this end, the image-acquisition device 100 comprises a C-arm fluoroscope 110 that may pivot about three orthogonal axes to allow imaging of a patient from several different angles. Typically, such a fluoroscope 110 includes an X-ray source 115 and an image acquisition module 120 mounted on opposite ends of a C-arm 125, as well as a table 130 where the patient lies. The portion of the patient""s body being imaged, typically the chest, is positioned between the ends of the C-arm 125. The image-acquisition module 120 converts x-rays that transit through the patient on the table 130 into electronic signals representative of 2-D images of the patient. The pivotable feature provides images from various perspectives, thereby allowing the reconstruction of a 3-D image of the patient from a series of successive 2-D images. This function is performed by a controller/processor 135, which is coupled to the image-acquisition module 120.
Tracking of the catheter 105 is accomplished by using a fixed transmitter 140 to transmit to a sensor 145 located on the catheter 105, thereby locating the catheter 105 relative to the transmitter 140. Optionally, a reference sensor can be placed on the patient, preferably the chest, to create a xe2x80x9cfixedxe2x80x9d space in combination with the transmitter 140 relative to other moving sensors. In this manner, the device 100 compensates for any movement of the patient, such as chest movement during the respiratory cycle. The sensor 145 typically comprises a housing that contains three pairs of electromagnetic sensing elements for the three orthogonal axes. In any event, the continuously changing position and orientation of the catheter 105 can be inferred from the electromagnetic signals transmitted by the transmitter 140 and received by the sensor 145. This tracking function is performed by driving circuitry 150 and reception circuitry 155, which are respectively coupled to the transmitter 140 and sensor 145, and the controller/processor 135, which controls the driving circuitry 150 and processes the signals received by the reception circuitry 155.
Thus, by determining the position and orientation of the catheter 105 relative to the frame of reference defined by the transmitter 140 and the optional reference sensor, the controller/processor 135 determines the position and orientation of the catheter 105 relative to the 2-D image acquired by the fluoroscope 110. The controller/processor 135 then synthesizes a combined image that includes both the 3-D image of the patient and an icon representing the catheter 105 positioned and oriented with respect to the 3-D image, and then displays this combined image on a monitor 158. In order to synchronize the acquired location of the catheter 105 with each 2-D image, the orientation of which changes as the C-arm 125 is rotated around the patient, another sensor 160, which is similar to the sensor 145 located in the catheter 105, is mounted on the C-arm 125. Electromagnetic signals received by the sensor 160 from the transmitter 140 are sent to reception circuitry 165, which is identical to the reception circuitry 155. The controller/processor 135 is coupled to this reception circuitry 155 and acquires the data therefrom to determine the orientation of the C-arm 125, and thus the orientation of the 2-D image, at any given time, so as to provide a means to synchronize the image of the catheter 105 with that of each 2-D image. Further details on the image-acquisition device 105 are described in PCT publication WO 00/10456, entitled xe2x80x9cIntrabody Navigation System for Medical Applications,xe2x80x9d and published on Mar. 2, 2000, which publication is fully and expressly incorporated herein by reference.
In order to securely mount the sensor 160 to the C-arm 125, certain constraints must be considered. First, as the sensor 160 serves as a fixed point of reference, it must be sufficiently secured to the C-arm 125, such that it does not move relative to the C-arm 125 when the C-arm 125 pivots. The sensor 160, however, should be easily engageable and disengageable from the C-arm 125 in order to replace the sensor 160 if desired. Secondly, as the sensor 160 functions by the reception of electromagnetic waves, it must not contact or be placed in proximity to any ferromagnetic material, such as steel or any other material or alloy containing iron, which would disrupt the magnetic field of the sensor 160.
Thus, an objective of this invention is to provide for a sensor assembly that detachably secures the sensor onto a C-arm, or some other pivotable image-acquisition device, without disrupting the sensor""s magnetic field.
The present inventions are directed to medical sensor assemblies that include sensors that can be detachably mounted onto a fluoroscopic mount, such as a C-arm. In accordance with a general aspect of the present inventions, a medical sensor assembly for use with a fluoroscopic mount comprises an electromagnetic sensor that is configured for outputting positional data relating to the fluoroscopic mount. The sensor includes a mount engaging element, and the sensor mount includes a sensor engaging element, both of which are configured to be removably mounted in an interference relationship with each other. The mount engaging element of the sensor can be a sensor housing, or alternatively, an element that is separate from the sensor housing. The sensor mount, which is composed of a non-ferromagnetic material, further includes a spacer for maintaining the sensor at a prescribed distance from the ferromagnetic fluoroscopic mount, thereby minimizing any adverse ferromagnetic effects on the sensor.
The sensor mount may be configured, e.g., in a front-mount arrangement, such that the sensor is mounted to the sensor mount in a direction perpendicular to the plane in which the sensor mount is mounted to the fluoroscopic mount. Alternatively, the sensor mount may be configured, e.g., in a side-mount arrangement, such that the sensor is mounted to the sensor mount in a direction parallel to the plane in which the sensor mount is mounted to the fluoroscopic mount.
The spacer can be configured to be permanently mounted to the fluoroscopic mount, e.g., by bonding or welding thereto. In this case, the sensor engaging element of the sensor mount can be permanently mounted to the spacer. For example, the sensor engaging element can be bonded or welded thereto, or can be formed with the spacer as a unibody structure. Thus, the sensor with the mount engaging element can be repeatedly attached to and detached from the fluoroscopic mount. Alternatively, the sensor engaging element, rather than the spacer, is configured to be permanently mounted to the fluoroscopic mount, e.g., by bonding or welding thereto. In this case, the spacer acts as the mount engaging element, in that it is configured to be removably mounted to the sensor engaging element, e.g., by using a hook-in-loop material, such as Velcro(copyright). The mount engaging element of the sensor can be permanently mounted to the spacer, e.g., by bonding or welding thereto. Thus, the sensor with the spacer can be repeatedly attached to and detached from the fluoroscopic mount.
In accordance with particular aspects of the present inventions, the sensor engaging element and mount engaging element may be variously designed. For example, the sensor engaging element of the sensor mount may comprise a pair of arms, and the mount engaging element of the sensor may comprise the sensor housing, which is received between the pair of arms in a snug relationship. As another example, the sensor engaging element may comprise a pair of arms, and the mount engaging may comprise a T-shaped housing that has a shaft configured to be inserted between the pair of arms and a pair of oppositely-extending sensor arms that are configured to be respectively disposed on the pair of arms. As still another example, the sensor engaging element may be an open cavity, and the mount engaging element may be a sensor housing or other member that can be received within the cavity in a direction perpendicular to a plane in which the sensor mount is mounted. As still another example, the sensor engaging element may be a conical cavity, and the mount engaging element may be a conical sensor housing that is received by the conical cavity. As still another example, the sensor engaging element may comprise means for receiving a clip, and the mount engaging element may comprise a clip that is received by the clip receiving means. As still another example, the sensor engaging element may comprise one of a cavity and member, and the mount engaging element may comprise the other of the cavity and member, with the cavity and member having substantially uniform and matching cross-sections, such that they can slidingly engage each other. As still another example, the sensor engaging element may comprise one of a snap protuberance and hole, and the mount engaging element may comprise the other of the snap protuberance and hole, with the protuberance and hole being capable of engaging each other in a snap-fit arrangement. As still another example, the sensor engaging element may comprise a flexible planar member, e.g., a hook-in-loop material, and the mount engaging element may comprise a rigid planar member, with the flexible planar member being configured to mount the rigid planar member to the sensor mount.